Andersons pediatric cardiology 774
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inpatientswithaninteratrialcommunicationhavebeensuggested.Themost
widelyacceptedexplanationpostulatesareciprocalrelationshipofchangesin
pulmonaryandsystemicvenousreturnwithrespiration.46
Themurmursassociatedwithanatrialseptaldefectaretypicallysoft.They
maybeabsentininfancyandearlychildhood,explainingtherelativelatenessof
diagnosisinmostindividuals.Itisextremelyuncommonforamurmurtoariseat
thesiteoftheinteratrialcommunicationitself,sincethereisusuallylittleorno
gradientacrossit.Instead,themurmursaregeneratedbyrapidbloodflow
throughtherightheartandthepulmonaryarterialbed.Almostallindividuals
withaclinicallyrecognizableatrialseptaldefecthaveasystolicejectionmurmur
atthehighleftsternalborder,whichisrelatedtorapidflowacrossthe
pulmonaryvalve.Themurmurisusuallysoft,andamurmurofgreaterthan
grade3to6shouldsuggestthepossibilityofaccompanyingpulmonaryvalveor
arterystenosis.
Mostindividualswithalargeleft-to-rightshuntthroughaninteratrial
communicationalsohaveasoftmid-diastolicmurmuratthelowerleftsternal
border.Thismurmurisalwayssubtleandisalmostneverrecognizedunless
specificallylistenedfor.Themurmuristhatofrelativetricuspidstenosisandis
generatedbyrapidflowacrossanormaltricuspidvalve.Unlikethemurmurof
organicorrelativemitralstenosis,thismurmurisnotlow-pitchedandrumbling.
Rather,itisofmediumpitchandisoftenscratchy.
Thephysicalfindingsassociatedwithaninteratrialcommunicationare
completelydifferentwhenthereispulmonaryvasculardisease.Withanincrease
inrightventricularpressure,theleftparasternalliftmaybecomemore
pronounced.Thewidthofsplittingofthesecondheartsounddecreases47andthe
intensityofthepulmonarycomponentincreasesinintensityinproportiontothe
degreeofelevationofpulmonaryarterydiastolicpressure.Ifpulmonary
hypertensionissevere,newmurmursofpulmonaryandtricuspidregurgitation
mayoccur.Themurmurofhypertensivepulmonaryregurgitationistypically
high-pitchedanddecrescendo,beingmaximalatthehighandmiddleleftsternal
border.Thismurmurisusuallyclinicallyindistinguishablefromthemurmurof
aorticregurgitationunlessthesecondheartsoundiswidelysplit,anditcanbe
appreciatedthatthediastolicmurmurbeginswiththesecondpulmonary
component.Themurmuroftricuspidregurgitationishigh-pitchedandsystolic;it
isusuallymaximalatthelowerleftsternalborder.Itmaybeeitherearlyor
pansystolic,anditmayincreaseinintensitywithinspiration,afeatureknownas
theCarvallosign.48
InvestigationsandDiagnosis
Electrocardiography
Normalsinusrhythmistheruleinchildhood,butatrialflutterorfibrillationis
seenwithincreasingfrequencyafter40yearsofage.ThemorphologyoftheP
waveisusuallynormalinovalfossadefects,butonereviewdemonstratedthat
thefrontalplaneaxisofthePwavewaslessthan15degreesinnearlyhalfof
sinusvenosusdefects,suggestingalowatrialfocus.49Inchildrenwithdeficient
atrialseptation,thefrontalplaneQRSaxisisalmostalwaysintherangefrom90
to170degrees,butintheadulttheaxismayshiftleftwardtotherangeof70to
90degrees.Althoughleft-axisdeviationoccurringinthesettingofanatrial
shuntstronglysuggeststhepresenceofanostiumprimumdefect,approximately
5%ofthosewithovalfossaandsinusvenosusdefectshavethisaxis.26,49Mildto
moderaterightventricularhypertrophyispresentinmorethanfive-sixthsof
patientsandisusuallymanifestedbyanRSR′pattern,or“crochetage,”inthe
rightprecordialandinferiorleads,respectively(seeFig.29.1).TheRorR′wave
rarelyexceeds15mmunlessthereissignificantelevationofpulmonaryvascular
resistanceandpulmonaryarterialpressure.14,33TheQRSdurationiseither
normalormildlyprolonged,rarelyexceeding0.11second.Completeright
bundlebranchblockisveryrareinchildhoodbutoccursinnearlyhalfofthese
patientsolderthan60years.32
Radiology
Thechestradiographshowsmildtomoderatecardiomegalyinmostpatients,but
upto17%haveaheartofnormalsizeeveninthepresenceofalargeleft-to-right
shunt.33,50Irrespectiveofwhetherornottheheartisenlarged,thereisalmost
alwaysanabnormalcontouraswellasalargerightatrium,rightventricle,and
pulmonarytrunkandadiminutiveaorta(seeFig.29.2).Pulmonaryvascular
markingsareusuallyincreasedwhentheratioofpulmonary-to-systemicflowis
2to1orgreater,butthevascularitycorrelatespoorlywiththemagnitudeofthe
shunt.51Oncepulmonaryvasculardiseasedevelops,thetypicalfindingsof
Eisenmengersyndromemaybepresent,withaneurysmaldilationofthe
proximalpulmonaryarteriesanddistaltaperingofthevessels.Inpatientswitha
sinusvenosusdefect,theremaybelocalizeddilationoftheproximalsuperior
cavalveinattheentranceoftheanomalouspulmonaryveins,givingthe
appearanceofahigher-than-normalvascularpedicleintherighthilum.Inmost
patientswiththistypeofdefect,theradiologicfindingsareidenticaltothoseofa
typicaldefectwithintheovalfossa.
Echocardiography
Echocardiography,particularlywhencombinedwithDopplerstudies,hasproved
tobediagnosticinthemajorityofpatientswithinteratrialcommunications.
Thesetechniquesallowaccurateassessmentofthesizeandlocationofthe
defect,aswellasthedegreeofrightventricularvolumeoverload.BoththeMmodeandcross-sectionalechocardiogramareusefulindetectingthemost
significanthemodynamiceffectofanimportantatrialshunt,namelyright
ventricularenlargement(Fig.29.14).TheclassicM-modeechocardiographic
findingsarenearlyalwayspresentwhenthereisalargeleft-to-rightshunt.Right
ventriculardimensionsareincreased,andthereisfrequentlyflattenedor
paradoxicseptalmotion(Fig.29.15).52–55Severalparametershavebeenusedto
judgethemagnitudeofleft-to-rightshunting,56,57butgiventhedecreasing
relianceonanexactshuntcalculationinclinicaldecision-making,theseare
rarelyusedinday-to-daypractice.
FIG.29.14 Parasternalshort-axissectionattheleveloftheleftventricular
(LV)papillarymuscles.Thecavityoftherightventricle(RV)issignificantly
enlargedinthesettingofamoderate-sizedovalfossadefect.
